The Galerie des Glaces at Versailles
The Hall of Mirrors, built between 1678 and 1684 to link the king's apartment to the queen's. The three hundred and fifty-seven mirrors were made in France at a moment when Venice guarded the technique jealously, which is part of what the room was built to demonstrate.
Versailles is usually described as a palace and is better understood as an instrument. The court was moved there in 1682 and roughly ten thousand people came with it; the daily ceremonial of rising, dining and retiring turned attendance on the king into the only route to favour, and the nobility that had fought the Fronde a generation earlier spent its energy on precedence instead. The Hall of Mirrors was where ambassadors were received and where that arrangement was displayed to outsiders. See Versailles as absolute monarchy engineered in stone and ritual.
CC BY-SA 3.0 — source (Wikimedia Commons). Free to reuse under the stated licence.